PPC: Fix AssertFunction.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1345223005

Cr-Commit-Position: refs/heads/master@{#30838}

src/ppc/macro-assembler-ppc.cc

@@ -2586,7 +2586,9 @@ void MacroAssembler::AssertFunction(Register object) {
     STATIC_ASSERT(kSmiTag == 0);
     TestIfSmi(object, r0);
     Check(ne, kOperandIsASmiAndNotAFunction, cr0);
-    CompareObjectType(object, r0, r0, JS_FUNCTION_TYPE);
+    push(object);
+    CompareObjectType(object, object, object, JS_FUNCTION_TYPE);
+    pop(object);
     Check(eq, kOperandIsNotAFunction);
   }
 }